PROVIDENCE, R.I. (AP) — Amid an investigation by the U.S. Securities and Exchange Commission about the state's bond offerings, Rhode Island's retirement board on Wednesday approved a new set of assumptions that estimates the state's unfunded pension liability is 27 percent higher than previously thought.

The changes also mean that taxpayers could be on the hook for at least $156 million more in contributions to the retirement systems for teachers and state retirees in 2013 alone.

The SEC has indicated it's interested in whether states are adequately disclosing pension liabilities, and it began an investigation in January into Rhode Island's disclosure practices. It is looking at the state's bond transactions since 2007. A larger unfunded pension liability can be more risky for bond investors and hurt the state's bond rating, which makes it more expensive to borrow money for projects such as roads and bridges.